The present invention relates generally to the manufacture of automotive engine components possessing non-round exterior shapes using a powder metallurgy process, and more particularly to the manufacture of camshaft lobes using a modified dynamic magnetic compaction (DMC) process.
Automotive engine camshaft lobes must endure significant and repeated mechanical loading under high-speed, high-temperature and tribologically-varying conditions. The use of conventional manufacturing processes, such as casting, forging or the like, tends to produce components which, while satisfactory from a load-bearing perspective, result in heavy, inefficient structures. Likewise, the use of conventional manufacturing approaches is not conducive to tailoring a particular material's desirable properties to discreet locations on a camshaft lobe. Furthermore, the use of DMC, which is taught in U.S. Pat. Nos. 5,405,574, 5,611,139, 5,611,230 and 5,689,797 (all of which are hereby incorporated by reference), while a valuable way to compact both metallic and non-metallic powders to achieve high-density components, has not hitherto been extended to camshaft lobes, gears or other non-axisymmetric (i.e., non-cylindrical) or otherwise irregularly-shaped components.
Camshaft lobes and other highly-loaded engine components could benefit from the strategic placement of materials into the lobe that can be tailored to the lobe operating environment. For example, surface portions (for example, the generally planar eccentric surfaces) of the lobe that are exposed to higher loads may benefit from harder or other more load-bearing materials that would not be needed in the generally axisymmetric portion of the lobe. Likewise, such materials could be used in the DMC process to give a particular shape to a formed component. Because such more robust materials may involve greater expense, weight or detrimental features, they may only be used sparingly. As such, it would be advantageous to develop ways to combine the efficient manufacturing attributes of DMC with the tailored structural properties of disparate constituent materials to fabricate structurally efficient components.